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Central Heating May Be Making Us Fat

Americans like to crank up the heat in the winter — and some scientists think it’s making us fat. Turn down the thermostat, they say, and you might lose a few pounds.

The link between ambient temperature and weight is not completely far-fetched. When we’re exposed to extreme cold, we shiver, an involuntary reaction that makes our skeletal muscles contract to generate heat, burning extra calories in the process.

And even in mildly cold conditions, like in a chilly room with the thermostat turned down to the lower 60s, people generate extra heat without shivering. The process, called non-shivering thermogenesis, may involve a substance called brown fat that adults carry in certain areas, like the upper back and side of the neck. Unlike regular fat, which stores excess energy and calories, brown fat acts like an internal furnace that consumes lots of calories, but it has to be activated first — and cold temperatures do that.

Now, in a provocative new paper, British researchers argue that rising indoor temperatures are contributing to obesity. The research team included scientists from several disciplines, including health psychologists, biologists and those who specialize in the effects of indoor environments.

The hypothesis was initially put forth several years ago in a paper listing 10 “putative contributors” to obesity, including environmental endocrine disruptors, pharmaceuticals that induce weight gain, sleep debt, older mothers having children and epigenetic changes, or environmental factors that influence the expression of our genes.

The newer paper, published this week in the journal Obesity Reviews, looked specifically at indoor temperatures. The researchers found that since central heating became commonplace in the 1960s, room temperatures have increased slowly but steadily in both the United States and Britain. In both countries, obesity has also been on the rise.

The average temperature of living rooms in Britain, around 64.9 degrees Fahrenheit in 1978, had risen to 70.3 degrees by 2008. Bedrooms, kept at 59 degrees in 1978, were up to 65.3 by 1996, the last year figures were available.

In the United States, living rooms have long been heated to just over 70 degrees in the winter, at least when the house is occupied. Bedroom temperatures continue to rise and were up to 68 as of 2005, from 66.7 in 1987.

“What’s particularly noticeable is that people are heating the whole of their house,” said Fiona Johnson, a research fellow at University College London and the paper’s lead author. “In the past they would heat the main living areas, and the bedrooms might be cold at night.” That means people no longer have to adjust to different temperatures as they move through the house.

In addition, most people get around town in heated cars, instead of walking, and children spend less time playing outdoors.

All this time spent in toasty interiors may be affecting the levels of brown fat we carry, Dr. Johnson said. “It’s kind of ‘use it or lose it,’ ” she said. “If you’re not exposed to cold, you’re going to lose your brown fat, and your ability to burn energy will be affected. But you can get it back.”

While we all start out with substantial amounts of brown fat as babies, “it gradually decreases over the life course,” she said. “But if it is needed — if we’re regularly exposed to cold — the body can actually generate more brown fat.”

That is not to say exposure to cold is a major driver of obesity: overeating and lack of exercise are the main causes.

But could lowering the thermostat make a notable difference in people’s weight?

“When we put people in a 60-degree room, they increase their energy expenditure by 100 or 200 calories a day if they’re in light clothing,” like hospital scrubs, he said. “They’re not shivering. They activate their brown fat.”

Over a period of several weeks, they will have burned an extra 3,500 calories, which translates into the loss of one pound. Wearing a sweater will dilute the effect.

The problem, Dr. Kahn said, is that “most people won’t stay at that temperature for very long.”

As the article points out, lower thermostats are not likely to cause any significant weight reduction. This is because most people are not likely to tolerate 60 degrees for very long, and even if they do they have on a sweater or are sleeping under a comforter. Thus, the example given of losing a pound over “several weeks” at 60 degrees is really a total folly. Further, there is no evidence provided that brown fat is linked in any way to obesity rates.

So this concept really is “far-fetched,” in contrast to TPP’s claim stated in her second paragraph. I now realize that she made that claim to induce us to read on, but it is disingenuous.

Editor’s note: The story is by Roni Caryn Rabin, not TPP, who is off this week; but thanks for your comment.

The problem is that sitting still in a cold room, say to read or study, just makes me feel chilled, depressed, and – hungry. I’m fine in a cool room as long as I’m moving around. But in a 60 degree room sitting still, my hands and feet turn to blocks of ice. Not very “homey”. I greatly dislike chilly offices for the same reason, and sometimes get sick from it, especially if it’s drafty as well.

While there’s something to be said for acclimation to the cold (maybe that’s the brown fat), there are still metabolic differences among individuals.

I don’t understand this statement: “When we put people in a 60 degree room, they increase their energy expenditure by 100 or 200 calories a day if they’re in light clothing,” like hospital scrubs, he said. “They’re not shivering. They activate their brown fat.”

I’m very thin and I am ALWAYS cold. I shiver constantly unless I’m extremely active or very bundled up. Shivering is quite unpleasant, and I try to avoid it. Does this mean I don’t have any brown fat? But if being cold and shivering creates it, wouldn’t I end up with more, given that I’m so cold all the time? I I’m just confused as to why despite a lot of exposure to the cold (we do keep our thermostats low, only heat parts of our large, drafty house, and maintain the bedrooms at 59 degrees), I never get to the point where I’m “activating my brown fat” and not shivering.

It’s quite convenient to believe that correlation implies causation, as the authors of the article clearly do. It allows one to make all sorts of clear statements that sound very convincing. In order to keep up this illusion, I believe we should ignore all data about rising obesity in the South Pacific and the American south, because in these places, central heating is not as important. Of course, the rising rates of obesity in India and Australia need to be ignored too, but that’s easy.

We should also agree not to discuss the relationship between wealth and obesity, and how wealth relates to access to central heating. Considering that would make things too confusing.

I’d like to add, that people who spend time swimming or even if they aren’t swimmers, just splashing around in cool swimming pools also loose this fat. Link it with true cardio swimming, and it’s a big part of why people who swim have “Swimmers’ ” build. And by cool, I don’t mean frigid. Even heated pools can have water that in spite of being comfortably warm to swim in, are non-the-less cool enough to trigger the body’s self heating mecahnism mentioned in this article. Now, am I going to go walk outside for an hour in 30 degree weather??? Boy do i wish I had that fortitude….

I’m really sick of these silly articles about health that rely on nothing more than a little bit of statistical correlation to “prove” a priorly held theory. One can easily manipulate just about any statistic and correlate to some health issue. Here’s a fun one:

“Is Greek style yogurt killing us? An article to be published this month in the scientific journal “Lactose” found that as american consumption of greek style yogurt increased form the 1960s to 2008, so did deaths due to gun violence.”

In the spirit of anecdotal commentary, I’ll add mine. I have programmed the thermostat to 57 at night and a toasty 63-64 during some daytime hourse. Might turn it up to a balmy 67 if we have guests at which point my ears start to feel uncomfortably warm. Based on the commentary, one might wonder how our ancestors (our parents, that is), survived through the dark, cold 60’s and 70’s. Our ancient ancestors (grandparents), likely stayed warm and relatively non-obese by shoveling coal into the water boiler in the basement. I will add that my wife and myself, remain close and svelte (if I say so myself) and have not acquired a buffalo hump of brown fat in the process.

We live in upstate NY in 4 bedroom house. We heat half the downstairs with a wood stove with central heat as a backup. That is our living area so we keep it at 60-65. The upstairs bedroom is only for sleeping, so it is kept at 45. You get used to it, especially if you spend part of every day outside skiing or snowshoeing. We save money and are doing our part to cut reliance on fossil fuels. This is how our parents and grandparents lived.

Sounds like BS to me. Virtually everyone I know who is fat (and I include myself) always has a problem with being too hot compared to others at the same temperature. I have kept my home @ 65 during the winter for years, and my bedroom @ 58-60 as I like the ambient air as cool as possible when I sleep, and in the summer it is difficult for me to ever be ‘too cool’. Yet I invariably lose weight in the summer, and gain weight in the winter.

I think there might be something in this, thouigh perhaps it’s only a transient effect. The new heating system in my building keeps my apartment warm but not hot. I can turn up additional heat but this kills off my ivy plant, so a week or so ago, I stopped doing it (wearing on an extra sweater if necessary). I weigh myself every morning. For the early part of this week, I ate more than I usually do, but didn’t put on any weight. Yesterday, I ate normally, and seem to have lost a pound. However, I am sure this is too good to last, as I suspect that my body will soon accommodate itself to the lower temperature.

I was in San Francisco 2 weeks ago and noticed people swimming in an aquatic park (part of the SF Bay) without wetsuits despite the water temperature being in the low 50’s. I was told that the swimmers tolerate the temperatures by building up “brown fat.”

“This effect was shown in short-term controlled human experiments [41,42] and the decreases in adiposity were evident in controlled animal experiments; these effects are widely exploited in livestock husbandry, where selecting the environment to maximize weight gain is critical. [43]”

It would be interesting to know whether what is needed is the whole-body chill, or just exposure to cold. Shoveling snow, it’s easy to spend an hour out in the cold with chilled extremities and a sweaty core. Cross-country skiing and biking are much the same. Seems like the exercise would confound any measurement of cold-effect.

We keep our apartment extremely cool during winter in order to save on the energy bill. As a result, I am cold all the time– and I do eat more because it helps me feel warmer. Under more comfortable circumstances, I’m sure I would be a lot thinner! Not to mention that when my room is uncomfortably cold, I don’t even want to get out of bed– and I’m in a lot bigger hurry to get back in it.

My home is heated via propane, the cost of which is astronomical. Therefore, for several winters now, the thermostat is set to 64 degrees 7AM to 10 PM and 60 degrees during the night – no exceptions. I am overweight and have seen no impact of these temperatures on my weight at all. But I will say that once you get used to lower temps (get a nice fleece vest and you’re good to go), other homes feel uncomfortably hot and stuffy. We are in the process of converting to a wood-fired outdoor boiler to eliminate the propane, but even then I doubt we will increase the thermostat temperatures, as we now enjoy the cooler air in the house. As a added benefit, we have experinced fewer colds and sniffles since we lowered the winter heat temps. I don’t know if there is a correlation but it is a fact that we are overall healthier (and sleep much better, too) with the cooler indoor temperatures.